Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Sibling Traversal

Julien Arseneau
seal-mask
.a{fill-rule:evenodd;}techdegree
Julien Arseneau
Full Stack JavaScript Techdegree Student 5,200 Points
Posted by Julien Arseneau
.a{fill-rule:evenodd;}techdegree
Julien Arseneau
Full Stack JavaScript Techdegree Student 5,200 Points

Can someone explain to me how to highlight an element?

The elements won't highlight.

app.js 
const list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let li = e.target.parentNode
    let  ul = li.parentNode
    ul.insertBefore.highlight
  }
});
index.html 
<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript and the DOM</title>
    </head>
    <link rel="stylesheet" href="style.css" />
    <body>
        <section>
            <h1>Making a Webpage Interactive</h1>
            <p>Things to Learn</p>
            <ul>
                <li><p>Element Selection</p><button>Highlight</button></li>
                <li><p>Events</p><button>Highlight</button></li>
                <li><p>Event Listening</p><button>Highlight</button></li>
                <li><p>DOM Traversal</p><button>Highlight</button></li>
            </ul>
        </section>
        <script src="app.js"></script>
    </body>
</html>

2 Answers

richporter
richporter
16,727 Points

For this challenge you need to add a class to an element using DOM traversal. The 'highlighting' is not really relevant.

Since we're not adding new nodes, we don't need the insertBefore method.

We need to know which button was clicked (e.target), then we use previousElementSibling to find whatever element is immediately before it (the p tag we need), then we access the list of classes it contains, then add the class of highlight to that class list.

const list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {

    e.target.previousElementSibling.classList.add('highlight');

  }
});